Apparatus for controlling a braking system

ABSTRACT

Apparatus for controlling a pneumatic brake system includes electronic control means which limits the maximum brake effort even when an external electrical power supply to the braking system is not present.

The present invention relates to apparatus for controlling a brakingsystem under circumstances including situations where the normalelectrical supply has failed.

[0001] According to the present invention, there is provided apparatusfor controlling a pneumatic braking system under emergency or securitybrake modes and providing a safe operating envelope for service brakemode, the apparatus including electronic control means which limits themaximum brake pressure even when an external electrical power supply tothe braking system is not present.

[0002] The apparatus could include additional pneumatic pressurelimiting means for maximum and minimum brake pressures in case offailure in a primary electro-pneumatic limiting means.

[0003] The apparatus could include means for providing a load weighsignal to increase the brake effort in proportion to vehicle load.

[0004] The apparatus could include means for providing a position codingsignal to select the characteristics of the limiter function independence on the vehicle type and bogie weight at the installedposition.

[0005] An independent electrical supply could be supplied from a localsupply or by an air to electrical converter directly from a pneumaticsupply.

[0006] An independent electrical supply could be generated by an air toelectrical converter which draws its pneumatic supply from one side orthe other of at limiter valve or alternatively exhaust air from brakeactuation means or from an air suspension system.

[0007] The present invention will now be described, by way of examplewith reference to the accompanying drawings, in which FIGS. 1, 2, 3, 4,5, 6, 7, 8, 9 and 10 are block diagrams of examples of apparatusaccording to the present invention.

[0008] Apparatus according to the present invention may operate inconjunction with a normal brake control system providing a safe envelopefor the normal system control.

[0009] Apparatus to be described by way of example are designed toprovide the following functions:

[0010] To ensure the pneumatic brake effort will not exceed a specifiedmaximum value under any circumstances.

[0011] To ensure that in an emergency situation the brake effort willrise to this designed maximum.

[0012] The maximum brake effort can optionally be adjusted in accordancewith vehicle loading so that the brake effort is increased as thevehicle load increases. (This ensures the stopping distance in emergencysituations is the same for empty and fully loaded vehicles).

[0013] The control and operation is carried out electronically, drivingnormal control valves when the service brake control system is unable toprovide that drive or has been deliberately disabled.

[0014] In the Figures, the same reference numerals are used to designatethe same items.

[0015] Referring first to FIG. 1, electrical power is supplied on a line1 to an emergency load limiter control 2, to which an electrical loadweigh signal on a line 3 and/or a position coding signal on a line 4 mayoptionally be supplied. Air from a main brake supply pipe 5 is fed to alimiter valve 6 leaving an exhaust outlet 7. Limiter valve 6 receives anelectrical signal from the emergency limiter control 2 via a line 8. Alimiter valve pressure sensor 9 supplies an electrical signal on a line10 to emergency limiter control 2. An output from the limiter valve 6 isfed to a service brake valve unit 11, having a service exhaust output 12and receiving an electrical signal from a service brake controller 13and having an output supply pipe 14 feeding air to one or more brakeactuators.

[0016] The optional input position coding signal on line 4 identifieswhich vehicle type and at which position on that vehicle the system isfitted. The position coding signal is used to select the characteristicof the limiter valve.

[0017]FIG. 2 differs from FIG. 1 in that a converter drive 15 suppliesair to an air to electrical converter 16 from main brake air supply pipe5. Electrical power is supplied on line 1 to emergency limiter control2. Electrical power from line 1 is also supplied to a converter drivecontrol 17 whose electrical output signal is used to control converterdrive 15.

[0018] In FIG. 3, exhaust air from the limiter valve 6 and/or exhaustair from the service brake valve unit 11 is fed to air to electricalconverter 16 which supplies electrical power on line 1 to the emergencylimiter control 2.

[0019] In FIG. 4, air to electrical converter 16 is connected in serieswith the limiter valve 6 and valve unit 11 in the pipe 14 to the brakeactuator(s) and supplies electrical power on line 1 to the emergencylimiter control 2.

[0020] In FIG. 5, air in a pipe 18 from an air suspension system is fedto air to electrical converter 16 which supplies electrical power online 1 to the emergency limiter control 2.

[0021] FIGS. 6 to 10 correspond with FIGS. 1 to 5 respectively with thedifference that the limiter valve 6 and the service brake valve unit 11are combined into a single control valve unit 19.

[0022] Operation of the limiter valve control would typically be:

[0023] The emergency limiter control 2 monitors the limiter pressuresensor 9 and increases or decreases the limiter valve control pressuredemand until the limiter pressure on line 10 equals the setpoint of theemergency limiter control 2.

[0024] If the limiter valve output pressure is low, the limiter valveinlet is opened, allowing air to flow from the main brake supply 5 tothe output.

[0025] If the limiter valve output is high, then the limiter valveexhaust is opened, allowing, air to flow from the output to the exhaust7.

[0026] This process is always available while sufficient pressure ispresent in the main brake supply pipe 5. Thus, it is possible for theapparatus to be used in emergency or security applications.

[0027] The service brake controller 13 provides the normal brake controlwhere the apparatus is operating from the usual electrical supplies, butis protected at all times to operate within the safe working envelopesupplied by the limiter valve.

[0028] In the apparatus of FIG. 1, 2, 3, 4 and 5, the limiter valve 6and the service brake valve unit 11 are separated. It is possible thatthese two valves could he combined into a single control valve unit 19as shown in FIGS. 6, 7, 8, 9, and 10.

[0029] In order to maintain full electronic control when the externalelectrical supply is not present, air to electrical converter 16 couldbe used. This could draw air from one of the following sources:

[0030] The main brake supply 5 (FIG. 2 or FIG. 7).

[0031] The limiter exhaust from 7 of the limiter valve 4 or the serviceexhaust from 12 of the service brake valve unit (FIG. 3).

[0032] The exhaust from 7 of the control valve unit 19 (FIG. 8).

[0033] The brake actuator supply pipe 14 (FIGS. 4 and 9).

[0034] Pipe 18 from the air suspension system (FIGS. 5 and 10).

[0035] In FIGS. 2, 3, 4, 5, 7, 8, 9 and 10, to reduce air consumptionconverter drive control 17 with a converter drive valve is added inseries with the air to electrical converter 16. Once the electricalpower supply on line 1 has reached the required voltage, the converterdrive control 17 switches the converter drive 15, breaking the airsupply to the air to electrical converter 16. Once the voltage drops toa lower defined level, the converter drive control 17 switches theconverter drive 15, reapplying air to the air to electrical converter16. However, in FIGS. 3, 4, 8 and 9, where the air to electricalconverter 16 draws its air supply from either the brake actuator side ofthe control valve 6 or the exhaust front 7, the converter drive 15 isnot necessarily required. The air consumption can be controlled byswitching the valve 6 or unit 19.

[0036] Alternatively, as in FIG. 5, the air to electrical converter 16can be arranged to receive its air supply from the converter drive 1 viapipe 18 from the air suspension system.

[0037]FIGS. 1, 2, 3, 4 and 5 show service brake valve unit 11 downstreamof the limiting valve 6, but equally the service brake valve unit 11could be fitted upstream of the control valve 6.

1. Apparatus for controlling a pneumatic braking system under emergencyor security brake modes and providing a safe operating envelope forservice brake mode, the apparatus including electronic control meanswhich limits the maximum brake pressure even when an external electricalpower supply to the braking system is not present.
 2. Apparatusaccording to claim 1, including additional pneumatic pressure limitingmeans for maximum and minimum brake pressures in case of failure in aprimary electro-pneumatic limiting means.
 3. Apparatus according toclaim 1 or 2, including means for providing a load weigh signal toincrease the brake effort in proportion to vehicle load.
 4. Apparatusaccording to claim 1, 2 or 3, including means for providing a positioncoding signal to select the characteristic of the limiter functiondependant on vehicle type and bogie weight at the installed position. 5.Apparatus according to claim 1, 2, 3 or 4, wherein an independentelectrical supply is generated by an air to electrical converterdirectly from the pneumatic supply.
 6. Apparatus according to claim 1,2, 3 or 4, wherein an independent electrical supply is generated by anair to electrical converter which draws its pneumatic supply from oneside or the other of a limiter valve or alternatively exhaust air frombrake actuation means or from an air suspension system.